(IDEX Online) - Amazon leapfrogged Costco and Tiffany last year to become the third biggest watch and jewelry retailer in the US.Its 2020 sales leapt by almost 40 per cent, from $1.62bn to 2.24bn as the pandemic forced more and more customer online.Signet, with almost 2,500 outlets, remained the biggest seller by far, according to National Jeweler magazine's The $100m Supersellers league table. But sales were down 13 per cent on the previous year to 4.84bn.Walmart was second-placed, with sales of 2.86bn, down marginally on its 2020 performance.Amazon jumped from fifth to third place. Costco remained in fourth position with sales of ?, ?1.63bn (down from $1.69bn).Richemont moved up from sixth to fifth place with sales almost unchanged - up from $1.54bn to $1.56bn.Tiffany & Co moved down the table from third place to sixth, as sales plunged from $1.66bn to $1.22bn.Macy's remained in seventh place, as sales fell from $1.5bn to $1.13bn.